Register

If this is your first visit, please click the Sign Up now button to begin the process of creating your account so you can begin posting on our forums! The Sign Up process will only take up about a minute of two of your time.

Follow us on Facebook Follow us on Twitter
Results 1 to 6 of 6
  1. #1
    Registered
    My Boats:
    1973 cary 33
    Join Date
    Feb 2005
    Location
    biloxi, ms
    Posts
    51

    Mercruiser 454 or 7.4 Serial numbers

    On StemtoStern.com, or Mercruiserparts.com, or other parts lookup websites, there is a range of serial numbers from about 0f800000 to 0k999999.

    If you were looking at stern drive big blocks, these numbers were identified as ........1996-97 454 Mag MPI (Gen IV)
    If you were looking at inboard big blocks, these numbers were identified as .........1996-97 7.4L MIE MPI (Gen IV).

    But they are all (stern or inboard) in the same category of numbers.

    Do all these engines have rectangle ports and HiPerf cam?
    What hp are these engines?
    Are they all the same (except for the bellhousing)?

    Some people say they are 300HP, some say that they are 385HP.

  2. #2
    Go Big or Go Home Platinum Member stageharbor's Avatar
    My Boats:
    78 cig 28 ss, 89 donzi 33zf
    Join Date
    Jun 2005
    Location
    Kennebunkport, Me.
    Posts
    187
    454 mag mpi is 385 hp 7.4 mpi is 310 i believe. the 7.4 model has weak internals. I do not know about the heads.

  3. #3
    Registered
    My Boats:
    1973 cary 33
    Join Date
    Feb 2005
    Location
    biloxi, ms
    Posts
    51
    The part numbers for the 7.4 MIE MPI are:
    Crank.............429-811551
    Head...............938827656
    Intake.............805233A6

    The numbers for the 454 Mag MPI are:
    Crank..............737-850477T
    Head...............938-827495T
    Intake..............805233A6

    So, the cranks are different.
    The Heads are different.
    But the intake is the same.
    Did Merc put a rectangle MPI intake on oval heads?

  4. #4
    Registered
    My Boats:
    1973 cary 33
    Join Date
    Feb 2005
    Location
    biloxi, ms
    Posts
    51
    How can these engines have different part number for heads but have the same intake?

  5. #5
    Registered Dave_N's Avatar
    Join Date
    Jan 2005
    Location
    Newport Beach,CA
    Posts
    573
    Quote Originally Posted by jerosejr View Post
    How can these engines have different part number for heads but have the same intake?
    The 7.4MPI's (pre L29) used the MPI intake with the retangular runners but it was bolted up to the small oval port heads. Seems crazy, but that's what they did.

    Dave

  6. #6
    Registered
    My Boats:
    1973 cary 33
    Join Date
    Feb 2005
    Location
    biloxi, ms
    Posts
    51
    Is this confirmed because there are a lot of engines for sale on OSO, Ebay, etc that have a serial number in this range and people are claiming 400 HP, probably because they figure that a Gen VI with rectangular MPI MUST be Hi Performance.


    Well, what about all the problems you see on this forum regarding fuel pooling, etc.
    Did Merc just decide this was not a problem?


Similar Threads

  1. 525SC Serial Numbers ???
    By G Man in forum General Q & A
    Replies: 5
    Last Post: 10-01-2007, 11:49 PM
  2. Mercruiser serial numbers
    By Pantera1 in forum General Boating Discussion
    Replies: 2
    Last Post: 05-02-2006, 03:50 PM
  3. serial numbers on motors
    By jr2 in forum General Q & A
    Replies: 5
    Last Post: 01-14-2005, 05:37 PM
  4. engine serial numbers
    By US1 Fountain in forum General Q & A
    Replies: 2
    Last Post: 05-15-2003, 09:41 PM
  5. Alpha serial numbers...
    By Iggy in forum General Q & A
    Replies: 2
    Last Post: 01-25-2002, 10:20 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
OSO Sponsor
OSO Advertisers


OSO Directory
All times are GMT -5. The time now is 01:53 AM.
Powered by vBulletin® Version 4.2.0
Copyright © 2014 vBulletin Solutions, Inc. All rights reserved.
Search Engine Optimization by vBSEO 3.6.1
Original Poster In Postbit provided by Original Poster In Postbit v1.0.0 (Free) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd. Runs best on HiVelocity Hosting.
Copyright 2011 OffShoreOnly. All rights reserved.